Food storage and cooling apparatus

ABSTRACT

This invention provides an improved food storage unit for keeping frozen and refrigerated food. The assembly includes a housing defining a cavity open from the housing along one of the sides of the cavity. Door means are releasably engageable with the housing across the one side of the cavity for closing the cavity opening. Gasket means cooperate between the door means and the housing for providing an essentially airtight seal between the door means and the housing in the closed position of the door means. Thermal insulation material is carried by the housing and by the door means for essentially fully enclosing the cavity in the closed position of the door means. Partition means are disposed in the housing for subdividing the cavity into first and second chambers. A receptacle is associated with the first chamber for receiving a predetermined quantity of solidified carbon dioxide. Thermal insulation material is provided in association with the partition so that the receptacle is thermally associated with the first chamber more intimately than with the second chamber. The predetermined quantity of solidified carbon dioxide, in conjunction with the thermal insulation material, is sufficient to maintain the first chamber at a temperature below 0* C. and the second chamber at a temperature above, but approaching 0* C. for a predetermined time under specified ambient temperature conditions.

United States Patent 1191 Knapp et al. I

[ 1 Apr. 2, 1974 i 1 FOOD STORAGE AND COOLING APPARATUS [75] 1 Inventors: Karl K. Knapp; Delbert R. Reedy,

both of Los Angeles, Calif.

[73'] Assignee: Kardel Products Corporation, Los

Angeles, Calif.

[22] Filed: May 15, 1972 [21] Appl. No.: 253,414

[52] US. Cl 62/384, 62/298, 62/457, 62/440, 62/447 [51] Int. Cl. F25d 3/12 [58] Field of Search 62/165, 166, 167, 168, 62/384, 457, 385, 386, 387, 388, 447

[56] References Cited UNITED STATES PATENTS 1,900,855 3 1933 Aylsworth 62/385 2,768,505 10 1956 Goodwin 62/384 1,951,679 3/1934 Sherrick 62/165 1,965,205 7 1934 Smith 62/166 2,011,881 8 1935 Stewart... 62 168 2,024,490 12 1935 Van lkC 62/388 2,039,334 5/1936 Nagy 62 388 2,056,731 10 1936 Lithgow.. 62 386 2,493,647 1 1950 Wagner... 62/168 2,143,239 1 1939 F0llZ....... 62 384 2,400,742 5 1946 016m 62/388 3,069,869 12 1962 Mueller 62 457 3,406,532 10 196 Round 62 457 Primary Examiner-William J. Wye Attorney, Agent, or FirmChristic, Parker & Hale [57-] ABSTRACT This invention provides an improved food storage unit for keeping frozen and refrigerated food. The assembly includes a housing defining a cavity open from the housing along one of the sides of the cavity. Door means are releasably engageable with the housing across the one side of the cavity for closing the cavity opening. Gasket means cooperate between the door means and the housing for providing an essentially airtight seal between the door means and the housing in the closed position of the door means. Thermal insulation material is carried by the housing and by the door means for essentially fully enclosing the cavity in the closed position of the door means. Partition means are disposed in the housing for subdividing the cavity into first and second chambers. A receptacle is associated with the first chamber for receiving a predetermined quantity of solidified carbon dioxide. Thermal insula tion material is provided in association with the partition so that the receptacle is thermally associated with the first chamber more intimately than with the second chamber. The predetermined quantity of solidified carbon dioxide, in conjunction with the thermal insulation material, is sufficient to maintain the first chamber at a temperature below 0 C. and the second chamber at a temperature above, but approaching 0 C. for a predetermined time under specified ambient temperature conditions.

14 Claims, 4 Drawing Figures PAIENIEDAPR 2:914 SL800 554 SHEU 1 OF 2 1 FOOD STORAGE AND COOLING APPARATUS FIELD OF THE INVENTION This invention pertains to food storage apparatus, and more particularly to such apparatus using passive resistance and latent heat control mechanisms for preserving frozen and refrigerated foodstuffs.

BACKGROUND OF THE INVENTION Description of the Prior Art: Travel trailers, camper units, camper vans and the like are experiencing increasing use as recreational vehicles in place of or as an alternative to tents on weekend or extended camping trips, for example. Since such vehicles are either towed by a pickup truck or automobile, for example, or directly or indirectly mounted to the chassis of a pickup truck, for example, the conventional source of power for operating the lights and appliances in such recreational vehicles is usually the power system of the vehicle itself. It is well known that the battery and ignition system of an automobile or pickup truck is initially designed and equipped for the purposes of operating the vehicle itself, rather than for the purposes of operating such auxiliary equipment as may be provided in the camper unit or the like. As a result, the perishable food storage facilities in such vehicles are either nonexistent or are of a type which do not require the use of electrical power derived from the vehicle ignition system. It is known to equip recreational vehicles with refrigerators or refrigerator-freezer units which operate on a thermodynamic cycle powered by an auxiliary electric storage battery or by natural gas, for example; such units are not preferred because of their expense, lack of reliability, and the safety hazards associated with them, but their existence in the marketplace does serve to emphasize the utility of the present invention. In general, therefore, to the extent that recreational vehicles of the types mentioned do include facilities for keeping perishable foods, the typical facility often relies upon the use of ice to maintain an insulated food storage chamber at a temperature approaching but above C. Such iceboxes, however, are not capable of freezing unfrozen foods products or of maintaining frozen food products in a frozen state for any significant period.

At present, there are commercially available many iceboxes which have been designed specifically for use in camper units, camper vans, travel trailers and the like. In general, the commercially available iceboxes are of generally standardized dimensions, and usually are rated at a capacity of four cubic feet; such iceboxes are also known as 75 pound iceboxes.

A need exists for a refrigerating and freezing food storage assembly useful in recreational vehicles and the like and capable of maintaining both frozen and unfrozen foods at the proper temperature for extended periods. Desirably, such an assembly should not be dependent on power derived either from the vehicle engine or its associated equipment, nor should the assembly rely on natural gas as a power source. Ideally, the desired refrigeration and freezing capability should be provided by a unit which is compatible with, insertable into and takes advantage of the structure of existing recreational vehicle iceboxes available for use with unfrozen perishable foods. It'h'as been ascertained that a sizable commercial market exists for products filling these needs.

SUMMARY OF THE INVENTION This invention provides an improved refrigerating and freezing food storage assembly which is simple, economic and efficient. One form of the invention is an insert unit which may be disposed in the ice storage area of commercially available recreational vehicle iceboxes for the purposes of converting the icebox to a refrigerator-freezer. The use of this insert unit increases the effective food storage volume provided in the icebox. The insert unit provides the desired refrigerating and freezing capabilities by the use of solidified carbon dioxide, commonly known as dry ice, which is available at reasonable cost. By its use of dry ice as the cooling medium, the insert unit avoids the problems attendant to the use of electrical or natural gas power systems. Also, because the unit relies upon the insulative characteristics of the conventional recreational vehicle icebox, it is compact, structurally simple, and reliable.

Generally speaking, this invention provides an improved refrigerating and freezing food storage assembly which comprises a housing defining a cavity therein. The cavity has an opening from the housing along the extent of one side of the cavity. Door means are releasably engageable with the housing across the one side of the cavity for closing the cavity opening. Gasket means cooperate between the door means and the housing for providing an essentially airtight seal between the door means and the housing in the closed position of the door means. Thermal insulation material is carried by the housing and the door means for essentially fully enclosing the cavity in the closed position of the door means relative to the housing. Partition means are disposed in the housing for subdividing the cavity into first and second chambers. Receptacle means are provided in association with the first chamber for receiving a predetermined quantity of solidified carbon dioxide. Thermal insulation material is also operatively associated with the partition means so that the receptacle is thermally coupled to-the first chamber more intimately than to the second chamber.' The predetermined quantity of solidified carbon dioxide which the receptacle is adapted to receive, in conjunction with the thermal insulation material, is sufficient to maintain the first chamber at a temperature below 0 C. and the second chamber at a temperature above, but approaching 0 C. for a predetermined time under selected ambiem p ure oalit ns.-

DESCRIPTION OF THE DRAWINGS The above-mentioned and other features of this invention are more fully set forth in the following description of presently preferred embodiments of the invention, which description is presented with reference to the accompanying drawings, wherein:

FIG. 1 is a front elevation view, with the door thereof open, of a conventional recreational vehicle icebox in which a freezer conversion insert unit according to this invention is disposed;

FIG. 2 is a cross-sectional elevation view of the insert unit shown in FIG. 1;

FIG. 3 is an enlarged fragmentary elevation view of the structure enclosed within the correspondingly numbered area of FIG. 2; and

FIG. 4 is an enlarged fragmentary elevation view of the structure enclosed within the correspondingly numbered area of FIG. 2.

DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 illustrates the use of a freezer conversion insert unit of this invention in the internal cavity 11 of a commercially available recreational vehicle icebox 12 having a door 13. Cavity 11 is of generally cubical configuration and is essentially closed on five sides by the icebox housing 14, i.e., the major portion of icebox 12, and is open across one entire side of the cavity to the exterior of the housing. Door 13 is mounted by suitable hinges 15 to the housing for movement into and out of closure relation to the housing across the open side of the cavity. A suitable gasket 16 extends around the periphery of the cavity opening for cooperation with the door in its closed position. When door 13 is closed relative to housing 14, cavity 11 is completely sealed except for the presence of asuitable water drain fitting (not shown) provided in the icebox for draining from the interior thereof such water as results from the melting of ice disposed in the upper portion of the icebox cavity. The top, bottom, side and back surfaces of cavity 11 are insulated by suitable quantities of thermal insulation material disposed within the hollow walls of housing 14, and door 13 is similarly insulated. The presence of insulation in housing 14 itself is not illustrated in FIG. 1, but thermal insulation 17 within door 13 is shown as typical of the insulation provided within housing 14.

Icebox 12 may be any one of a number of commercially available recreational vehicle iceboxes, preferably of the 4 cubic foot size. Since iceboxes are marketed under a number of trademarks and trade names, including the trademarks MOBILAIRE, TRAVLER, CEON, MARVEL, MEYNELL, TU-CO, A.F.P., and GRAND PRIX. In such iceboxes, it is typical for the opposing side wall surfaces 18 and 19 of cavity 11 to define a plurality of aligned horizontal ledge projections 20, 21, 22 and 23. Projections 20 and 21 open in one direction along the height of cavity 11, whereas projections 22 and 23 open in the opposite direction along the height of the cavity. Projections 20-23 are usually symmetrically disposed about the middle of the height of the cavity so that icebox 12 has no true top or bottom. Rather, the icebox may be disposed either as shown in FIG. 1 to provide a left-hand opening icebox or upsidedown relative to FIG. 1 to provide a righthand opening icebox. Ledge projections 21 and 22 are provided for supporting an ice shelf(not shown) which, when positioned in snug mating contact between projections 21 and 22, subdivides the cavity into an upper ice compartment and a lower refrigerated food storage compartment. Depending upon the disposition of the icebox, ledge projections 20 or 23 may be used, if desired, to support a removable shelf within the food storage compartment.

Except for the inclusion of freezer insert unit 10 therein, the subject matter illustrated in FIG. 1 is commercially available equipment which is not per se a part of this invention but which constitutes the environment within which the insert unit is used to advantage. The insert unit is shown in FIG. 1 with its door 40 removed.

In addition to side wall surfaces 18 and 19, icebox cavity 11 has top, bottom and back surfaces 24, 25 and 26, respectively.

Referring to FIG. 2, insert unit 10 has a preferably unitary body 30 which is of generally cubical configuration to provide constant thickness walls around a generally cubical cavity 31 defined therein. The cavity has an open front end. Preferably, body 30 is fabricated of rigid polyurethane foam material of suitable thickness which, in a presently preferred embodiment of the insert unit, is approximately three-fourths inch thick. It will be understood however that any rigid or semi-rigid closed pore synthetic foam material may be used to define body 30. The outer surface of body 30 defines five of the six outer surfaces of unit 10. A liner shell 32 is formed, as by injection molding or vacuum forming techniques, of a suitable plastic material, to mate essentially exactly with cavity 31. Thus, liner 32 defines a structurally strong and moisture impermeable lining around the top 34, bottom 35, side 36, and back 37 surfaces of a cavity 33 within unit 10. The liner may be omitted where body 30 is fabricated of a self-skinning synthetic foam material. The liner 32 preferably is of uniform thickness throughout and is configured to define an upwardly open ledge projection 38 which extends into cavity 33 along the back and over a major portion of the front-to-back dimension of the opposite side surfaces of the cavity at a uniform distance below the top surface 34 at about the middle of the height of the cavity. Ledge projection 38 is provided for removably receiving and suppori'z-ing an upwardly open, but otherwise enclosed, dry ice receptacle 39 in the upper portion of cavity 33.

A door assembly 40 is connected at its lower end, for example, to the lower portion of body 30 by suitable hinges 41; see also FIG. 3. The door has inner and outer shells 42 and 43 which are spaced from each other over a major portion of their area but which are peripherally hermetically sealed together. The space between the opposing surfaces of the door shells is filled with a quantity of thermal insulation material, preferably. A resilient gasket 45 is carried in a recess 46 defined around the inner periphery of the door to cooperate with body liner 34 around the perimeter of the open front end of cavity 33 when the door is closed, as shown in FIG. 2. A manually operable latch lever 47 (see FIG. 4) is carried by a horizontal fulcrum pin 48 at an upper central location on the outer surface of the door adjacent an access recess 49 defined by the door outer shell. Latch lever 47 is configured to cooperate with the rear face of a keeper lip 50 defined by a stationary latch member 51 extending forwardly over the central portion of the open front end of cavity 33. Latch lever 47 and keeper lip 50 cooperate to provide a latching function for the door relative to body 30 when the door is forced sufficiently toward body 30 about hinges 41 to produce moderate compression of gasket 45. The gasket thereafter maintains the engagement of the latch lever and of the keeper lip until the latch lever is manually operated in the manner apparent from FIG. 4. Dry ice receptacle 39 is so sized that when it is engaged on ledge projection 38 in the manner shown in FIG. 2, the forward end of the dry ice receptacle is disposed closely adjacent the inner surface of the closed door. In this manner, the door functions to maintain the dry ice receptacle in a predetermined position within cavity 33. Also it is preferred that receptacle 39 be sealed as tightly as possible against the door and the body liner.

When the dry ice receptacle is disposed in the upper portion of cavity 33, it divides the cavity into an upper dry ice chamber 53 and a lower frozen food storage chamber which have approximately equal volume.

Preferably, the capacity of the dry ice receptacle is adequate to receive from 25 to 35 pounds of dry ice.

To install insert unit in icebox 12, thereby to convert the icebox from a refrigerator to a refrigeratorfreezer, the ice shelf normally disposed between icebox ledge projections 21 and 22 is removed and the conversion unit is inserted into the upper portion of icebox cavity 11. The conversion unit is sized to occupy somewhat less than one-half the volume of icebox cavity 11. The conversion unit is maintained in the extreme upper portion of cavity 11 by suitable fasteners which conveniently take the form of two pairs of adjustable-length brackets 56 (see FIG. 1) which are interposed between the lower corners of body 30 and the upper extent of the lower ones of ledge projections 21 or 22. In some cases, the body itself may be contoured to register with appropriate ones of ledge projections 20, 21, 22 or 23, or it may be rested on the ice shelf if one is prepared to accept the usable space reduction inherent in this mounting method. I v

The ice supporting shelf normally installed in icebox l2 completely fills that horizontal space of cavity 11 which has its upper and lower limits defined by the upper and lower extremities of ledge projections 21 and 22. It will be observed from FIG. 1 that the usable refrigerated volume of cavity 11, ie., that portion of cavity 11 not occupied by freezer conversion insert 10, is greater than the volume which would normally exist in the lower portion of the icebox cavity if the ice supporting shelf were present. It is apparent, therefore, that the use of insert unit 10 in icebox 12 increases the usable refrigerated storage volume available in the lower portion of icebox cavity 11. The insert 10 provides additional frozen food storage capacity in the frozen food chamber 54 within the insert.

When insert unit 10 is installed in icebox 12, the lower portion of body 30 provides a thermally insulated partition between frozen food storage chamber 54 and the refrigerated food storage chamber. The result is that dry ice receptacle 39, because of the partition and the insert door 40, is thermally more intimately coupled to the frozen food storage chamber than to the refrigerated food storage chamber. Therefore, dry ice in the receptacle is effective to maintain the frozen food storage chamber at a lower temperature, below 1 C., than the temperature, above but approaching 0 C, which is obtained in the refrigerated food storage chamber.

The thermal insulating properties of insert unit 10 per se are defined in combination with thermal insulating properties of icebox 12 in conjunction with the amount of dry ice which may be disposed in dry ice receptacle39 during use of the conversion unit as installed in icebox 12. The insulative characteristics of insert 10 are balanced to the insulative characteristics of icebox 12 so that, as dry ice disposed in the insert unit sublimes, frozen food compartment 54 and its contents are maintained at a temperature well below freezing, and the lower portion of icebox cavity 11 is maintained at a temperature of about 40 F. for from 3- 42 to 4 days in the presence of ambient temperatures of about 78 F. The freezer compartment, ie., frozen food storagechamber 54, has its temperature controlled by passive mechanisms, including the latent heat of fusion of the dry ice disposed in receptacle 39 and the heat transfer rates of the insulation of insert l0 itself and of icebox 12.

At atmospheric pressure, the sublimation temperature of dry ice is approximately -l09 F. Under conditions of thermal equilibrium, the heat lost from insert 10 to icebox cavity 11 must equal the quantity of heat lost from the icebox cavity to the exterior of the icebox; this is true since-insert unit 10 is disposed wholly within icebox cavity 11. If it is desired that the refrigeration space (i;e., the lower portion of icebox cavity 11) be maintained at a temperature of 40 F. when the ambient temperature is 78 by reason of dry ice disposed in receptacle 39, it can be shown that under conditions of thermal equilibrium a change of 4 F. would be expected in the temperature of the refrigeration space .from each 5 F. change in ambient temperature. Al-

though the reasons for the same are not presently understood, it has been found during testing of freezer conversion insert units like that described above (ie., insert units useful in 4 cubic foot recreational vehicle iceboxes) that the actual temperature change in the refrigeration space is approximately 3 F. for every 5 F. change in ambient temperature, and that this is true for the ambient temperature range between about F. and about F. The combination-of this discovery with the thermal damping associated with the sensible and latent heat capacity of the refrigerated foodstuffs results in a food cooling system which keeps the refrigerated food in compartment 11 colder than wet ice in the original utilization of item 12, and does not freeze the refrigerated food under the surrounding temperature is low enough, long enough that even the relatively expensive refrigerators (absorption and compression thermodynamic cycles) would also begin to freeze the refrigerated food. At the same time this new system keeps frozen food in chamber 54 frozen under all extremities of ambient temperature, and at much higher 1 temperatures than the prior refrigerators can keep frozen foods frozen in their freezer compartments. That is, it has been found that, in practice, freezer conversion insert units for recreational vehicle iceboxes constructed according'to the foregoing description are more efficient than is indicated by a theoretical analysis of the operation of the inserts under conditions of thermal equilibrium. The desired temperature is maintained substantially constant in the lower portion of cavity 11 until about 5 pounds of dry ice remains in receptacle 39, and as the last 5 pounds or so of dry ice is used, the temperature in the cavity rises slightly. It has been found that the extent to which the desired temperature is maintained constant in the cavity is enhanced by sealing the receptacle as closely as possible between door 40 and the interior of body 30. Also, the desired temperature control of the insert unit is surprisingly insensitive to the amount of surface area presen ted by the dry ice.

Workers skilled in the art to which this invention pertains will realize that the present invention has been described above with reference to specific'presently preferred embodiments of the invention merely for the purposes of example and illustration. Such workers will appreciate that the organizational, geometric, dimensional and thermodynamic relationships described above may be varied without departing from the scope of this invention to produce food storage containers and the like tailored to other thermal and usage conditions. For example, the principles illustrated by the foregoing description of insert unit as used in icebox 12 may be applied to advantage in an upright refrigerator-freezer unit having separate access doors to the refrigerated and frozen food storage compartments, or in a top-opening campers or sportsmans refrigeratorfreezer chest. Accordingly, the foregoing description should not be considered as limiting the scope of this invention.

What is claimed is:

1. An improved refrigerator and freezer food storage assembly comprising a housing defining a cavity therein, the cavity having an opening from the housing along the extent of one side thereof, door means releasably engageable with the housing across the one side of the cavity for closing the cavity opening, sealing means cooperating between the door means and the housing for providing an essentially'airtight seal between the door means and the housing in the closed position of the door means relative to the housing, thermal insulation material carried by the housing and the door means for fully enclosing the cavity in the closed position of the door means relative to the housing, thermal insulating partition means in the housing for subdividing the cavity into first and second chambers, receptacle means for receiving a predetermined quantity of solidified carbon dioxide, means mounting the receptacle means in the first chamber in operative thermal association therewith, the mounting means and the receptacle cooperating for removability of the receptacle means from the first chamber through said cavity opening, thermal insulation material operatively associated with the partition means over the entire extent of the partition means between the first and second chambers, said predetermined quantity of solidified carbon dioxide in conjunction with the thermal insulation material being sufficient to maintain the first chamber at a temperature below 0 C. and the second chamber at a temperature above but approaching 0 C. for a predetermined time when a predetermined ambient temperature exists outside the housing.

2. Apparatus according to claim 1 comprising a thermally insulated openable container removably disposed in the cavity in an upper portion thereof and defining said first chamber therein and the partition means, the receptacle means comprising a pan removably disposed in the container and dividing the first chamber into an upper coolant compartment and a lower frozen food storage compartment.

3. Apparatus according to claim 2 wherein the container has a body defined principally of a unitary mass of rigid closed pore synthetic foam material.

4. Apparatus according to claim 2 wherein the housing and the door means therefor comprise an insulated icebox for recreational vehicles and the like.

5. Apparatus according to claim 4 wherein the cavity has opposing side wall surfaces configured to define support means for an ice shelf transversely of the cavity at substantially the midheight of the cavity, and means coupled between the container and the support means for positioning the container in the cavity in the absence of engagement of an ice shelf with the support means.

6. Apparatus according to claim 2 wherein the insulation and configuration of the container is defined with relation to the housing thermal insulation material and the heat transfer characteristics of the housing to provide a thermal response characteristic in the second chamber of substantially 3 F. temperature change for each 5 F. temperature change in ambient temperature through an ambient temperature range of from about 60 F. to about F. when solidified carbon dioxide is present in the receptacle means.

7. Apparatus according to claim 6 wherein the container and housing heat transfer characteristics are defined to provide a steady state temperature of substantially 40 F. in the second chamber when ambient temperature is substantially 78 F. and solidified carbon dioxide is present in the receptacle.

8. In an icebox for recreational vehicles and the like including an insulated housing defining a cavity therein and an insulated door hinged to the housing for movement into and out of a closed position across an open side of the cavity, the improvement in an insert unit mountable in the icebox cavity for converting the icebox to a refrigerator-freezer, the insert unit comprising a body defined principally of a thermally insulating material and defining a chamber therein which is fully closed except for being open to the exterior of the body across a side of the cavity, a thermally insulated door connected to the body for movement into and out of a closed position across the open side of the cavity, a receptacle removably disposed in an upper portion of the chamber for receiving a predetermined quantity of solidified carbon dioxide, the remainder of the chamber being adapted to receive foodstuffs, and means for mounting the insert body in the upper portion of the icebox cavity, the body and the door therefor being sized to be disposed in the icebox cavity in the closed position of the icebox door, the insulative characteristics of the body and of the door therefor being proportioned relative to the insulative characteristics of the icebox'for creating and maintaining in the cavity outside the body a temperature of about 40 F. under ambient temperature conditions of about 78 F. when solidified carbon dioxide is received in the receptacle.

9. Apparatus according to claim 8 wherein the icebox cavity has opposing side walls defining aligned projections adapted for receiving and supporting an ice shelf, and wherein the means for mounting the insert body in the cavity comprises means cooperating between the body and said projections.

10. A conversion unit for converting a wet ice food cooler, having a unitary ice and food receiving cavity and an ice support shelf removably supported on projections extending from side walls of the cavity for supporting a quantity of ice in an upper portion of the cavity, to a refrigerator and freezer food storage device, the conversion unit comprising a housing defining therein a chamber having permanently closed top, bottom, back and side surfaces and a front opening, door means releasably engageable with the housing for closing the chamber front opening, gasket means cooperating between the doormeans and the housing for providing an essentially airtight seal between the housing and the door means in the closed position of the door means relative to the housing, a quantity of thermal insulation material in the door means and in the housing around the closed surfaces of the chamber, receptacle means removably disposed in the chamber in an upper portion thereof and occupying only a portion of the volume thereof for receiving a predetermined quantity of solidified carbon dioxide, the housing with the door means therefor being sized to be disposed wholly within the cavity of the cooler in an upper portion of the cavity, said predetermined quantity of solidified carbon dioxide in conjunction with said thermal insulation material being sufficient to maintain the chamber and contents thereof at a temperature below C. for a predeterm ined time when a predetermined ambient temperature exists outside the housing, the insulation associated with the housing being defined and proportioned with respect to the insulation of the cooler sufficiently that said predetermined quantity of solidified'carbon.

dioxide is effective to maintain the portion of the cooler cavity not occupied by the housing, when the housing is disposed in the cavity, at a selected temperature above but approaching 0 C. for said predetermined time when said predetermined ambient temperature exists, and means engageable with the housing for cooperation with the cooler ice shelf support projections for supporting the housing in the uppermost portion of the cavity.

11. A conversion unit according to claim wherein the housing with the door means therefor has an overall volume less than the volume of the coolercavity above the ice shelf projections andwherein the means en-- I gageable with the housing for supporting the housing is arranged for supporting the housing above the cooler ice shelf support projections whereby, when the housing is supported in the cavity from said projections, the cavity belowthe housing defines a greater food storage capacity than when the ice support shelf issupported on said projections.

12. A conversion unit according to claim 10 wherein said selected temperature is about 40 F and said, predetermined ambient temperature is about 78 F.

13. A conversion unit according to claim 12 wherein said predetermined time is on the order of 3- /2 to 4 ay Y 14. A conversion unit accordingto claim 12 wherein the insulation associated with the housing is proportioned and defined relative to the insulation of the icebox such that the temperature in the cavity outside the housing changes about 3 F. for each change of about 5 F. in the ambient temperature. 

1. An improved refrigerator and freezer food storage assembly comprising a housing defining a cavity therein, the cavity having an opening from the housing along the extent of one side thereof, door means releasably engageable with the housing across the one side of the cavity for closing the cavity opening, sealing means Cooperating between the door means and the housing for providing an essentially airtight seal between the door means and the housing in the closed position of the door means relative to the housing, thermal insulation material carried by the housing and the door means for fully enclosing the cavity in the closed position of the door means relative to the housing, thermal insulating partition means in the housing for subdividing the cavity into first and second chambers, receptacle means for receiving a predetermined quantity of solidified carbon dioxide, means mounting the receptacle means in the first chamber in operative thermal association therewith, the mounting means and the receptacle cooperating for removability of the receptacle means from the first chamber through said cavity opening, thermal insulation material operatively associated with the partition means over the entire extent of the partition means between the first and second chambers, said predetermined quantity of solidified carbon dioxide in conjunction with the thermal insulation material being sufficient to maintain the first chamber at a temperature below 0* C. and the second chamber at a temperature above but approaching 0* C. for a predetermined time when a predetermined ambient temperature exists outside the housing.
 2. Apparatus according to claim 1 comprising a thermally insulated openable container removably disposed in the cavity in an upper portion thereof and defining said first chamber therein and the partition means, the receptacle means comprising a pan removably disposed in the container and dividing the first chamber into an upper coolant compartment and a lower frozen food storage compartment.
 3. Apparatus according to claim 2 wherein the container has a body defined principally of a unitary mass of rigid closed pore synthetic foam material.
 4. Apparatus according to claim 2 wherein the housing and the door means therefor comprise an insulated icebox for recreational vehicles and the like.
 5. Apparatus according to claim 4 wherein the cavity has opposing side wall surfaces configured to define support means for an ice shelf transversely of the cavity at substantially the midheight of the cavity, and means coupled between the container and the support means for positioning the container in the cavity in the absence of engagement of an ice shelf with the support means.
 6. Apparatus according to claim 2 wherein the insulation and configuration of the container is defined with relation to the housing thermal insulation material and the heat transfer characteristics of the housing to provide a thermal response characteristic in the second chamber of substantially 3* F. temperature change for each 5* F. temperature change in ambient temperature through an ambient temperature range of from about 60* F. to about 100* F. when solidified carbon dioxide is present in the receptacle means.
 7. Apparatus according to claim 6 wherein the container and housing heat transfer characteristics are defined to provide a steady state temperature of substantially 40* F. in the second chamber when ambient temperature is substantially 78* F. and solidified carbon dioxide is present in the receptacle.
 8. In an icebox for recreational vehicles and the like including an insulated housing defining a cavity therein and an insulated door hinged to the housing for movement into and out of a closed position across an open side of the cavity, the improvement in an insert unit mountable in the icebox cavity for converting the icebox to a refrigerator-freezer, the insert unit comprising a body defined principally of a thermally insulating material and defining a chamber therein which is fully closed except for being open to the exterior of the body across a side of the cavity, a thermally insulated door connected to the body for movement into and out of a closed position across the open side of the cavity, a receptacle removably disposed in an upper portion of the chamber for receiving a predetermined quantity of solidified carbon dioxide, the remainder of the chamber being adapted to receive foodstuffs, and means for mounting the insert body in the upper portion of the icebox cavity, the body and the door therefor being sized to be disposed in the icebox cavity in the closed position of the icebox door, the insulative characteristics of the body and of the door therefor being proportioned relative to the insulative characteristics of the icebox for creating and maintaining in the cavity outside the body a temperature of about 40* F. under ambient temperature conditions of about 78* F. when solidified carbon dioxide is received in the receptacle.
 9. Apparatus according to claim 8 wherein the icebox cavity has opposing side walls defining aligned projections adapted for receiving and supporting an ice shelf, and wherein the means for mounting the insert body in the cavity comprises means cooperating between the body and said projections.
 10. A conversion unit for converting a wet ice food cooler, having a unitary ice and food receiving cavity and an ice support shelf removably supported on projections extending from side walls of the cavity for supporting a quantity of ice in an upper portion of the cavity, to a refrigerator and freezer food storage device, the conversion unit comprising a housing defining therein a chamber having permanently closed top, bottom, back and side surfaces and a front opening, door means releasably engageable with the housing for closing the chamber front opening, gasket means cooperating between the door means and the housing for providing an essentially airtight seal between the housing and the door means in the closed position of the door means relative to the housing, a quantity of thermal insulation material in the door means and in the housing around the closed surfaces of the chamber, receptacle means removably disposed in the chamber in an upper portion thereof and occupying only a portion of the volume thereof for receiving a predetermined quantity of solidified carbon dioxide, the housing with the door means therefor being sized to be disposed wholly within the cavity of the cooler in an upper portion of the cavity, said predetermined quantity of solidified carbon dioxide in conjunction with said thermal insulation material being sufficient to maintain the chamber and contents thereof at a temperature below 0* C. for a predetermined time when a predetermined ambient temperature exists outside the housing, the insulation associated with the housing being defined and proportioned with respect to the insulation of the cooler sufficiently that said predetermined quantity of solidified carbon dioxide is effective to maintain the portion of the cooler cavity not occupied by the housing, when the housing is disposed in the cavity, at a selected temperature above but approaching 0* C. for said predetermined time when said predetermined ambient temperature exists, and means engageable with the housing for cooperation with the cooler ice shelf support projections for supporting the housing in the uppermost portion of the cavity.
 11. A conversion unit according to claim 10 wherein the housing with the door means therefor has an overall volume less than the volume of the cooler cavity above the ice shelf projections and wherein the means engageable with the housing for supporting the housing is arranged for supporting the housing above the cooler ice shelf support projections whereby, when the housing is supported in the cavity from said projections, the cavity below the housing defines a greater food storage capacity than when the ice support shelf is supported on said projections.
 12. A conversion unit according to claim 10 wherein said selected temperature is about 40* F. and said predetermined ambient temperature is about 78* F.
 13. A conversion unit accordinG to claim 12 wherein said predetermined time is on the order of 3- 1/2 to 4 days.
 14. A conversion unit according to claim 12 wherein the insulation associated with the housing is proportioned and defined relative to the insulation of the icebox such that the temperature in the cavity outside the housing changes about 3* F. for each change of about 5* F. in the ambient temperature. 